Magnet



Sept. 14 1926. v v1,599,516

Hx sa FOLKER MAGNET Filed July 14. 3.922 s sheets-sheet 2 rtw.. ifo-I imi i Iii;

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/ha ATTORNEY Sept. 14 1926.

H. S. FOLKER Filed July 14. 1922 3 Sheets-Sheet 5 Patented Sept. 14,1926.

UNITED sTArasf PATE NT" OFFICE.

novi/"ARD s. FOLKER, kOFMILL VALLEY, CALIFORNIA, AssIGNoR To yTHENATIONAL SAFETY APPLIANCF. COMPANY, 0F SAN FRANCISCO, CALIFORNIA, AConroRA- TION OF CALIFORNIA.

Application filed July 14,

This invention relates to magnetic structures, and, more particularly,to an Improved track magnet adapted to be positioned' between the tracksof a railroad and, through changes in its magnetic field,tocon trol theoperation of a brake control mechanism of' a passing train.

In devices of' this type, the track magnet has heretofore been formed ofa permanent magnet and an electromagnet, the polarities of which Wereopposed to each other, the brake control mechanism being oper-ated bythe magnetic influence ofv the permanent magnet (when the electro-magnetWas de-encrgized. Owing to the comparatively short distance or shortlength of the track over Which they magnetic influence or field extendedin magnets of this type, and the correspondingly short period of timethis magnetic influence rwas exerted on .the brake con trol apparatus ofrapidly moving trainspthe operation of the brake control mechanismtended to become uncertain as the speed of the tiains increased. This vvassomewh'at augmented by any irregularities in the distribution of themagnetic flux and the-tendency of the permanent magnets to become weakerupon standing especially as the permanent magnets were notv providedWith a closed circuit of iron. u

An object ott' the present'inve'ntion is. to provid-e; a track magnetcapable ofexerting' a uniform magnetic influence upon a moving;` elementresponsive to magnetic Influences for a suic'ient space to controlVrapidly moving trains.

Another object of the present invention 1s to provide a permanent magnethaving a symmetrical magnetic field of any desired length and a fixedelectromagnetic means by which the field ofthe permanent magnetstructure may be modified in intensity as desired Without distortion ofthe symmetrical distribution ofthe magnetic field.l

A; further object of the invention isto provide a controlling means. fora permament magnet structurewhich, when ener-k gized, exerts astrengthening influence upon the magneto-motive force of the magnetmembers, and which, when not energized, provides a path of relativelylow reluctance' in the circuit of'themagnet members, to assist kinpreserving the magnetism ofthe-permanent magnets;

MAGNET.

1922. Serial No. 574,920.

A still further object of the invention is to provide a permanent magnetstructure which will produce a magnetic field of the desiredcharacteristics, and an electro-magnetic means Which will modify suchmagnetic field with a minimum energy input;

Still further objects of' the invention are to provide a simple andruggedy construction of the above class having no moving parts, toprovide a permanent magnetic circuit substantially closed with iron, buthaving an external leakage field of any desired extent, and to provide atrack magnet for operating train control mechanism upon moving trains,through which a magnetic field uniformly distributed along the axis ofthe track is provided' and an electro-magnetic means associatedtherewith and capable oit' being controlled by railway signal systems toneutralize the ield of said' permanent magnet to prevent the operationof said traincontrol mechanisms. y

lVith these and other objects in view the `invention comprises themechanism described and set forth inthe following speci'- fication andclaims.

The various featuresof the invention are illustra-ted in theaccompanying drawings, infwhich, A

Fig. l is a plan view of ay track magnet embodying a form oftheinvention and a section of' track .showing its position thereon.

Fig. 2- is a view in side elevation of the niagnet and portion of trackshown in Flgel. A

Fig. 3 is aplan View of the track'magmeans of Which is arranged to becharged with one polarity and the other with thel opposite polarity bypermanent magnets in such a manner as tofprovide a substantiallyuniform' magnetic potential throughout the length ot the eqnalizingmeans. .-'t number of electro-magnets are so arranged with relation tothe magnetic equalizing' means, that when energixed, they neutral L theniagnetic potential ot the equali.- ig means and at all times Yform withthe squaliA 'n means and permanent magnets sul itially closed magneticcircuit of iron. he inagnetie equalizing means is preferably formed ofa. pair et bars of iron er other suitable magnetic material the desiredlength, between which are positioned alterantely the permanent magnetsand the eleetromagnets, the positiye or north poles of all o' thepermanent magnets and the negative or south poles ot' the cores oit theelectromagnets being attached to one oi the bars and the op posite polesot the permanent magnets and electro-magnet cores being connected to theother bar.

The electro-n'iaguets are normally not energized. lilhen the electro-magets are not energized the uniform potential the equa izer bars producesIa. in erin iield in the atmosphere above the cture. It is this fieldthat is utilized to act -I1pon the control Valve upon the moving' t1. ito produce a control operation. When it is desired to pass the controlvalve over the structure Withouteliiectupon the control Valve, theelectro-magnets must be energized to neutralize, or .modity, themagnetic potential in the equalizer bars so that the iield above thestructure resulting from this potential will be Zero. or of such slight.alue as to produce no etiieift upon the control Valve. rJfhe cores oithe ereetroanagnets torni a part or" the magnetic circuit Whether or notthe electro-magnets are energized.

Referring more particulr-.rly to the accompanying draWings` a pair oi'magnetic equalizing bars l and l2 ot sott iron, adapted to be positionedbetween tracks 1l, are charged with opposite polarities by means otpermanent magnets lli, 1S. 2O and 22 spaced through the length olf thebars, 'our magnets being shown in the embodiment oit/the inventionillustrated in the drawings. For this purpose, the positive or northpoles ot' each orC the magnets ire rigidly mounted on, or connected to,`one of the bars, as 'tor example, bar l0, by means ot' clips 2lpre'terably ot non-magnetic material, and scren'threaded bolts, 2G, andthe other or south poles are similarly connected to the bar 12. Throughthe arrangement et the permanent magnets relatively to the equalizer'bars, the bar l0 is charged inductively with one polarity and the bar l2is charge-d inductively With the opposite polarity.

The magnetic charges of the bars l0 and l2 are neutralized or modiiiedby means oit electro-magnets 2*?, 3@ and Si lit-ably spaced along thelength oi the bars which, when energized, have a polarity opposite tothat of the permanent magnets lt), i8, and Q2. To this end, eachele.,ti'oim1gnet is provided with a soit iron core 34; the ends ot whichare mounted in pole pieces 3G, preferably of high permeability by meansot a pressed fit and by peening the ends el the cores over the polepieces, and are supported on the bars l0 and l2 by means of bolts 38 ofnonmagnetic material extending through holes in the pole pieces and thebars. The pole pieces 3o are also preterably spaced from the bars l0 and'l2 by spacing means 39 of brass or other nonemagnetic material toobtain the desired proportioning el' the magnetic flux between the coresci the electro-magnets and the air aboye the efpializing bars. Eachelertreanagnet is provided with a Winding LO connected in an electriccircuit in Such a manner that each electro-magnet has a polarity oil thesame direction as each of the other elrctro-rnagnets and ol a directionopposite that ot the permanent magnets 1G, 1S, 2O and Thus in thepresent embodiment, the positive, or north poles ot the electroanagneare adjacent the bar lil and the negative, or south poles are adjacentthe bar l0. The end electro-magnets 2S and 32 are spaced nearer i1ie endpermanent magnets 16 and respec iyely, than the intermediate permanentand electromagnets are to each other in order to obtain a more uniformdistribution or" the magnetic potential along the equalizing bars l0 andl2.

A suitable Wiring arrangement for energizing the electro-magnets isillustrated diag 'animaticallyv in the accon'ipanying drawings in whichthe windings are connected by Wires ll in series between the terminalsot' a source of electricity 4t2, such as a battery olf suitable type.The degree of magnetization may be controlled by adjusting the currentpassing through the wind` ings by means of a variable resistance orrheostat 4:41, to permit the magnetism of the electro-magnets toneutralize the magnetic force ot' the permanent magnets. A switch s@ isalso provided in the electric circuit Which may be opened or closed by arailu'ay signalling mechanism to control the l magnetization et theelectro-magnets and .the operation o the control device, the

switch being opened to ile-energize the electro-magnets when a train isto be stopped and closed When a train is permitted to pass.

The permanent magnets 1G, 1S, 2() and may be ol any* vsuitableconstruction. In the preferred embodiment ot' the invention they areformed oi. a number of bars 48, which may be straight, or horse shoe orother suitable shape and which are held in spaced relation by means otend clamps 49, preferably ot non-nnignetie material and by spacingmembers 50, also preferably of non-magnetic material inserted betweenthe bars.

. mamie The bars 48 are made of a material which retains itsmagnetization, such for example as hard steel.

The windings of the electro-magnets are made of insulated wire wound onthe cores 34 impregnated with an insulating conipound and retained onthe cores by means of discs 52 ot non-conducting material which formspool ends for the windings. The windings are covered and protected bymeans of cylindrical casings 54 or housings of non-magnetic materialslightl spaced fromv the outer layerof` the win ings and closed by endcaps 56 of non-magnetic material hermetically sealed on the ends of thecasings and holding the cores and casings in spaced relation. The spacebetween the winding and the wall of the casing is filled withinsulatingr material 58.

The operation of the apparatus isbriefly as follows: The permanentmagnets 16, 18, 20 and 22 tend to magnetize the bar 10 by induction withone polarity uniformly throughout its entire length and to magnetize theother bar 12 uniformly with .the opposite polarity. The magnetisminduced under normal conditions in the bars 10 and 12 by the permanentmagnets 16, 18, 2() an 22 is neutralized by the electro-magnets 28, and32, which, when energized, have a magnetism of the opposite polarity tothat of the permanent magnets and of approximately the same strength sothat, under these conditions no magnetic field is created above themagnet structure. When the brake mechanism of a passing train is to beoperated, the switch 46 is opened and the electro-magnets 28, 30 and 32become lle-magnetized through the stopping of the electric current. Thebars 10 and 12 thereupon become charged nduct-ively by the permanentmagnets.. The soft iron cores ofthe electroiiiagnets then act as keepersfor the permanent magnets through which the magnetic Circuit .iscompleted or closed and -a return path for the magnetic flux from thepoles of the permanent magnets is formed. Sufiicentreluctance isprovided in this circuit by the non-magnetic spacers 39 between the polepieces 36 of the electro-magnet cores and the bars 10 and 12 to cause apart of the flux to pass through the atmosphere above the magnet deviceand form a magnetic field of sufficient strength to operate the brakecontrol mechanism of a passing train.

The strength of the electric current through the electro-magnets 28, 3()and 32 is so adjusted by means of the variable resistance or rlieostat44, that the resulting inagnetic strength of the electro-magnets isequal to the strength of the permanent magnets, or the current may beincreased to produce a magnetic strength slightly greater than that ofthe pern'iancnt magnets and thereby rethe magnet structure may befurther adjusted by varying the thickness of the spacing elements 39between the pole pieces of the magnets and the equalizing bars, andthereby adjusting the reluctance to magnetic `flux of the path throughthe electro-magnet cores.

Since the flux between the equalizing bars will divide between theelectro-magnet cores and the air path inversely to the reluctance ofthese paths, by increasing the reluctance through the core path by theinsertion of i thicker spacing elements a larger portion of the fluxwill be diverted to the air above the structure, thereby increasing thestrength of the magnetic field through which the brake control devicepasses,

Since the greater the flux produced by apermanent magnet, the longerwill it retain its inagnetomotive force, the positioning oft' the polepieces of the electromagnets in close spaced relation with theequalizing bars maintains a relatively large flux and thereby aids thepermanent magnets to retain their magnetism.

By means of the present invention, therefore, a magnetic field of anydesired length and of a uniform strength throughout, except at theextreme ends, is provided, thus enabling it to exert a suflicentlysustained action to operate a passing brake control device regardless ofits speed. The strength of this field may, moreover, be varied withoutdistortion.

Having described the invention, what I claim and desire to secure byLetters Patent is 1. A device of the kind described which comprisesmagnetic equalizing bars, permanent magnets adapted to magnetize saidbars with opposite polarity uniformly throughout their lengths,electro-magnets adapted to neutralize the magnetization of said barsuniformly throughout their lengths, cores of low reluctance in saidelectro-magnets adapted to form a return circuit for the magnetic fluxof said permanent magnets and means for inserting a desired additionalreluctance in said return circuit.

2. A device of the kind described which comprises a pair of equalizingmeans permanent magnetic means arranged to induce a magnetic charge ofone polarity uniformly in one of said means and a magnetic charge of theopposite polarity in the other of said means, a return circuit of lowreluctance betvveen said means and means for increasing` the reluctanceof said return circuit to a desired amount.

3. fr device ot the lind described which comprises a pair ot' spacedbars ot high magnetic permeahilitv, a number ot spaced iernianentmagnets havingpoles o't one polarity adjacent one of said bars and polesot' the opposite polaritjr adjacent the other of said bars7 a number oieelectroinagnets having cores extendingY substantially i'rom one bar tothe other, pole pieces supporting the ends of said cores and supportedby said bars, inserts et' comparativeijv high reluctance betvveen saidpole pieces and said bars and an electric circuit adapted to magnetizesaid electroemagncts oppositely to said per-- manent magnets.

i device oit the kind described which comprises a pair et magneticequalizing means, permanent magnets adapted to induce magnetism of onepolarityY in one et said means and magnetism o'l the opposite polarityin the other ot' said me s. magnets adapted to induce magnet t of theopposite polarity to that ot said pe manent magnets and means tor varvistrength of said electro-magnetic etle 5. A device et the kind describedivi comprises a pair ot equalizing bars, a i Y ralitjfv of groups ofpermanentlj'nu bars` said groups being spaced at 1 i intervals along'the lengths ot said bar-- iinpart opposite polar-ities to the saidequalizingbars, and a plu'ality ot electromagnets, one less in numberthan the said groups et' permi-inentlj7 inagnetized bars) arrangedalternateljv to said groups uniform intervals, the said intervals beine'longer than the intervals between said groups, the said electromagnietswhen ene ized having,y polarities opposite to those ot the permanentljvvmagnetized bars in said groups, the end electromagnets beingr spacedcloser to the end than to the intermediate groups.

' 6. A device ont the liind described which comprises a pair ofequalizing bars, a plurality of groups of permanentlymagnetized bars7said `groups beingT spaced at uniform intervals alongr the lengths otsaid equalizing bars to impart opposite polarit'es to said equalizingbars, and a pluralityoteleetronuignets arranged alternately to saidgroups of permanentljv magnetixed liars, the said electroni-aguets whenenergiced having polarities opposite lo those ot the permanentlymagnetized bars in said groups and being situated closer to the saidgroups at the end of the said equalizer bars than to the intermediate`groups.

7. A magnetic device according; to claim 6, in which n'ieans foradjusting the magnet reluctance are provided in the circuits ot' theelectro-magnets.

8. A device of the kind described which comprises a pair oi equalizingmeansr` permanent magnetic means arranged to induce a magnetic charge ofone polarit-jY uniformly in one ot said means and a magnetic charge etthe opposite polarity in theother ot' said means, a return magneticcircuit betnce'i said means,v and means for adjusting the reluctance ot'said return circuit.

A device of' the kind described which prises a pair of equalizing bars,a plui oi groups ot' permanent magnets spaced at intervals alongr thelengths ol, said equalizing hars to impart opposite polarities to thesaid equalizing bars1 and a pluu ralitj.: oi electro-magnets spaced atintervals along` said equalizing bars:7 the said electroenagnets whenenergized having@ polarities opposite to those o'i` the permanentmagnets. the end electro-inaggnets being' spaced closer to the end thanto the intermediate `groups ot' permanentmagnets.

l0. A magnetic device according to claim 9 in which means lor adjustingrthe iii-ag netic reluctance are provided in the circuits ot theelectro-magnets.

In Witness whereof I have hereunto set my hand at San Francisco,California this (th day of July, 1922.

HOVARD S. FOLKER.

